Alex continues to slowly organize

Tropical Storm Alex continues to slowly grow more organized as it steams away from Mexico's Yucatan Peninsula. Satellite loops show that Alex's heavy thunderstorms continue to increase in areal extent, and low level spirals bands are slowly building to the south and north. The clockwise flow around an upper-level high pressure system a few hundred miles west of Alex is bringing about 15 knots of wind shear to the storm, which is slowing intensification. Heavy thunderstorm activity is limited on the storm's northwest side, thanks to the shear and some dry continental air flowing off the coast of North America. Sea Surface Temperatures are very warm, 29°C. The latest Hurricane Hunter center fix, at 12:07 pm CDT, showed a central pressures of 990 mb, a 1 mb rise in six hours. Top winds were holding steady near 60 mph. Alex has stalled out the last few hours, as it began to "feel" the trough of low pressure to its north breaking down the high pressure ridge that has been pushing the storm to the west-northwest. This stall has allowed the storm to churn up cold water from the depths, which is probably interfering with development. Satellite loops show that Alex has a very large circulation covering about 2/3 of the Gulf of Mexico. We can expect that should Alex become a Category 2 or stronger hurricane, its storm surge will affect a much wider stretch of coast than Hurricane Dolly of 2008 did.

Figure 1. Afternoon satellite image of Alex.

Track forecast for AlexThe latest 12 UTC (7am CDT) runs of our most reliable computer models have come into much better agreement. A consensus forecast arrived at by averaging together most or all of the tracks of our top models--the GFS, ECMWF, GFDL, NOGAPS, HWRF, UKMET, and GFDN--is pretty much what NHC always uses as the basis of their forecast. This consensus forecast has narrowed in on the region just south of the Texas/Mexico border as being the most likely landfall location, with the usual cone of uncertainty surrounding it. The computer model that had been making the northernmost landfall predictions, the Canadian model, is now projecting a landfall 100 miles south of the Texas/Mexico border. There has been a general southward shift of the models in their latest runs, and the most northerly landfall location, near Port Mansfield, is now being predicted by the HWRF model. The earliest landfall time is Wednesday morning, and the latest is Thursday morning. Which model should you trust? Last year, the best performing models at the 3 day forecast period were the GFS, Canadian, ECMWF, and GFDL.

With steering currents relatively weak, the uncertainty in landfall location is high. The average error in an NHC 72-hour track forecast last year was 230 miles, which is about the distance from Brownsville to Port O'Connor. Consider also that the NHC cone of uncertainty is the region where 2/3 of the time (using the last 5 years of statistics) the center of a storm will go. Forecast errors tend to be equally large along track (speed errors) and cross-track (deviations from side-to-side), so that means that about 20% of the time a storm will not be in the cone of uncertainty. Given the slow motion of Alex and the recent uncertainty of the computer models, people living just beyond the edge of the cone of uncertainty should not be confident yet that Alex will miss them.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 10am CDT (15 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 67% chance of tropical storm conditions (winds 39+ mph), 16% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

Uncertainty in the NHC Cone of UncertaintyA research project funded by NOAA known as the Joint Hurricane Testbed has produced a remarkable number of tools now in operational use at the National Hurricane Center to improve hurricane forecasts and warnings. One of these projects, called "Prediction of Consensus TC Track Forecast Error and Correctors to Improve Consensus TC Track Forecasts", was an effort by Dr. Jim Goerss at the Navy Research Lab to improve the accuracy of the NHC "cone of uncertainty" (AKA the "Cone of Death") showing where a storm is expected to track 2/3 of the time. The radius of the circles that make up the cone are based on error statistics of the official NHC forecast over the past five years. We can expect in certain situations, such as when the models are in substantial disagreement, a consensus forecast made using these models will have much greater than average errors. Since the NHC typically bases their forecast on a consensus forecast made using a combination of reliable hurricane forecasting models, it is instructive to view the "GPCE" (Goerss Prediction Consensus Error) circles to see if the uncertainty cone should be smaller or larger than usual. The consensus forecast I'll look at is called "TVCN", and is constructed by averaging the track forecasts made by most of (or all) of these models: GFS, ECMWF, NOGAPS, GFDL, HWRF, GFDN, and UKMET. In the case of this morning's 12 UTC (7am CDT) June 28 run of these models, here is what the radius of the "cone of uncertainty" should be, in nautical miles:

So, the GPCE error estimates are showing that the latest forecasts for Alex out to 72 hours are 4% - 17% higher in uncertainty than average. The 4 - 5 day forecasts are 32% - 49% more uncertain than average--but of course, we expect Alex to be inland at those times.

Intensity forecast for AlexAlex is currently over a region of ocean with relatively low total ocean heat content (about 10 - 30 kJ/cm^2). By Tuesday and Wednesday, the heat content will increase to 40 - 70 kJ/cm^2, which is high enough to allow Alex to rapidly intensify. Wind shear is currently a moderate 15 knots, and is projected by the SHIPS model to decrease to the low range, below 10 knots, on Tuesday and Wednesday. The combination of low wind shear and high ocean heat content should allow Alex to intensify into a hurricane. NHC is giving Alex a 78% chance of being a hurricane on Wednesday morning, and a 16% chance it will be a major hurricane at that time. Water vapor satellite images, though, show plenty of dry air over Texas and the adjoining waters, and this dry air may turn out to be a significant detriment to Alex. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. Another factor limiting Alex's intensification may be its slow forward speed. Alex has already stalled out once, and may stall out later in its path, as well. A stalled-out storm tends to pull up cold water from the depths, limiting intensification. In short, Alex has the potential to intensify into a major hurricane, but there are enough roadblocks that I give a 20% chance of this happening.

Elsewhere in the tropicsNone of the reliable computers models is calling for tropical storm formation over the the next seven days in the Atlantic.

Wind and ocean current forecast for the BP oil disasterIt currently appears that Alex will not directly affect the oil slick location, other than to bring 2 - 4 foot swells to the region on Wednesday. However, because Alex is such a deep low pressure region, strong southeast winds of 15 - 25 knots will blow over the oil slick region today through Wednesday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border.

Portlight continues its Haiti responseHurricane season is here, and Haiti is not ready. Over 1.5 million Haitians are living outside in tents or under tarps, and are highly vulnerable to a hurricane. Portlight is working on constructing steel shelters out of shipping containers for homeless Haitians, as detailed in the Haitian Relief Recap blog post. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to Portlight's efforts in Haiti.

Figure 3. Still frame from the remarkable video taken inside the Haitian Presidential Palace during the 2010 earthquake.

To remind people of just how devastating the earthquake was, the Haitian government released a video earlier this month showing the inside of the Haitian Presidential Palace during the mighty Haitian earthquake.

Next postDr. Rob Carver is planning on making a post late tonight, and I'll have an update by 9:30am CDT on Tuesday.

My personal opinions, I think there will be a landfall on the Upper Texas Coast-Southwestern LA Coast,or 50 Miles on either side. That my cone, I have been saying that for the last 3 days, That's my story & I am sticking to it. Those who have been keeping up with the blogs, I have already given my reasoning many post ago,But as of now looking at all the data, I do beleive this is very possible. I maybe totally wrong, but I have been wrong before so.. We Shall See

Quoting MechEngMet:Okay all you science majors out there, riddle me this. If a large rotating mass is positioned on a rotating sphere (something like, oh say Alex on Earth for instance) with minimal to no steering influence, what is it's resulting motion likely to be?

Get a Tye-dye shirt creation platform (a.k.a. a record player on speed) and gently drop a marble on it with a little lateral momentum, while it is in motion while recording with a high frame rate camera. Playback in slow-mo and you'll see just what is going on with coriolis.

Quoting MechEngMet:Okay all you science majors out there, riddle me this. If a large rotating mass is positioned on a rotating sphere (something like, oh say Alex on Earth for instance) with minimal to no steering influence, what is it's resulting motion likely to be?

Quoting Clearwater1:For all of those that insisted that Brownsville and that area of Tx was ground zero, early on. . . good job. Now Hunker Down, for God's sake.

brownsville isnt ground zero but they arent out of the woods yet.... they will probably get TS force winds mostly in feeder bands only. That's cause the system is big. The main hurricane force winds will be 100- 150 miles further south.Landfall will be around 23.3-23.8N

Its so huge it take the winds time to catch up with the pressure, this storm is huge , like a typhoon one would see out in the western pacific , just wait til it really starts to get its act together and its gonna take the longest route to shore in my opinion.This could be one for the books!

Quoting MechEngMet:Okay all you science majors out there, riddle me this. If a large rotating mass is positioned on a rotating sphere (something like, oh say Alex on Earth for instance) with minimal to no steering influence, what is it's resulting motion likely to be?

Quoting DestinJeff:Post 1697 shows my point about XTRP very well. We tend to quickly respond with "Xtrp is not a model." Understood, it isn't. But it is telling in a different way.

The angle between xtrp and ofcl is now roughly 45 degress at the axis. That means something. That means short term movement has not been as forecasted. Look for ofcl at 11 EDT to close that gap by shifting right.

I agree with the point you are making. We saw that with Bill most of the way across the Atlantic last year. The models were constantly calling for a curve to the North, but it just plowed west and the models would be re-adjusted with their curve right ahead of it again. XTRP was the best "model" for a good bit of time, LOL!

Okay all you science majors out there, riddle me this. If a large rotating mass is positioned on a rotating sphere (something like, oh say Alex on Earth for instance) with minimal to no steering influence, what is it's resulting motion likely to be?

Quoting sarahjola:i think people need to calm down. this is all opinion, and if you want to just listen to the nhc then go on their web site. why come to a blog that has people giving their opinion, and take personal offense to people's opinion? it makes no sense. the blog is for everyone who has an opinion. i'm not saying leave, but i am saying stop complaining cuz everybody don't have the same opinion as you or the nhc. we come here to kick ideas around, give opinion, and if possible teach each other a thing or two. storms are unpredictable. the forecast has changed more than once from nhc. it will continue to change until it makes landfall. storms change course all the time. no reason to call people ignorant. if everyone was the same this world would suck!:)i am an adult, and i will conduct myself as one. i come here to get the different aspect from people and look at satellite and then maybe even give my own opinion. i would not ever call someone ignorant for having an opinion different than mine. its weather it will do what it wants not what statistics tell it to do. i will come back later and hopefully people aren't bickering about opinions on weather.:)